Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N63/00—Biocides, pest repellants or attractants, or plant growth regulators containing microorganisms, viruses, microbial fungi, animals or substances produced by, or obtained from, microorganisms, viruses, microbial fungi or animals, e.g. enzymes or fermentates
  • A01N63/30—Microbial fungi; Substances produced thereby or obtained therefrom
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S435/00—Chemistry: molecular biology and microbiology
  • Y10S435/8215—Microorganisms
  • Y10S435/911—Microorganisms using fungi

Definitions

• This invention relates to a method for the biological control of weeds and, more particularly, to such a method using a fungal pathogen.
• Lamb's-quarters ( Chenopodium album L.) is an annual weedy plane with a wide distribution throughout the world. It can be found growing from lat 70°N to lat 50°S and is one of the five most widely distributed plants in the world. The plant is a very successful colonizer of disturbed soil and is a serious weed problem in cultivated crops such as sugar beets, corn, soybeans, and cereal crops.
• the morphological features of the plant are quite variable.
• the plant is an erect annual herb that grows up to 2.5 metres in height.
• the ridged, branching stems often have reddish parallel stripes arranged length-wise.
• the simple, alternate leaves have shapes that range from ovate-lanceolate to rhombic-lanceolate. Although there are no distinct lobes, the leaves can have up to 10 shallow lobes.
• the leaf surface is glabrous with a mealy, farinose texture. No stipules are present.
• the inflorescence, a spike pannicle has green perfect flowers with 5 sepals and no petals.
• the plants are wind-pollinated, with large plants producing up to 500,000 seeds.
• lamb's-quarters forms a large proportion of the residual seedbank in the soil.
• the plane has no special method of dispersal other than shedding of seeds around the parent plant. Therefore, lamb's-­quarters is normally found in patches that are often dense and uniform. If not controlled, the weed can very quickly become troublesome and competitive in the crop. Apart from the competition that it offers the crop, the weed can be poisonous to some livestock if large quantities are consumed. The seed is also found as impurities in crop seeds and the pollen can cause allergies.
• lamb's-quarters is easily controlled through cultural and chemical methods. For example, preplant incorporated, pre-emergence, and post-emergence applications of atrazine provide excellent control of lamb's-quarters in corn. Shallow mechanical cultivations are also used to assist in the control of small seedlings.
• problems with some of the control methods Apart from the general concern with chemical pesticide contamination of the environment, there are more specific concerns with triazine resistant lamb's-quarters plants. These resistant plants have become a problem in North America and western Europe. In western Europe triazine resistance has also been reported in the related species, C. polyspermum and C. ficifolium . When this resistance appears, other control measures are necessary such as alternative herbicides, greater use of crop rotation, and mechanical cultivation. However, these other control measures are not always possible or desirable. With the increased use of minimum tillage techniques, less reliance is placed on mechanical cultivation and crop rotation is not as easy to use. Therefore, greater use of chemical herbicides is often necessary for weed control.
• the pathogen can also be used to control other Chemopodium weed species that are susceptible to the pathogen.
• the pathogen can also be used in combination with chemical herbicides and/or other pathogens to enhance the control of lamb's-quarters and/or other weeds.
• the fungal pathogen, Ascochyta hyalospora was discovered on the research station of Macdonald College in Ste-Anne-de-Bellevue, Quebec in September, 1985.
• the original isolate was obtained from diseased leaf tissue and labelled ChA 02A.
• the isolation technique was a commonly used method in which pieces of diseased leaf tissue are immersed in 70% ethanol for 30 seconds, transferred to 2% sodium hypochlorite for approximately 60 seconds, and rinsed twice with sterile distilled water. After drying on filter paper, the leaf pieces are placed on Potato Dextrose Agar (PDA) medium. For storage, the isolated strain was grown on PDA in a glass storage vial.
• PDA Potato Dextrose Agar
• ChA 02H is a combination of three single conidia isolates of ChA 02A.
• ChA 02W has a mycelial transfer from the advancing edge of an Ascochyta colony growing from a piece of leaf tissue infected with the ChA 02A strain.
• ChA 02FF and ChA 02EE are single conidial strains isolated from ChA 02W. All strains are subcultures of the original isolate, ChA 02A.
• the pathogen When used in laboratory tests, the pathogen was found to damage or kill lamb's-quarters without harming common agricultural crop plants.
• the fungus has been shown in the tests to be capable of heavy defoliating a lamb's-quarters plant of any age as well as infecting the stems of young seedlings.
• Foliar infection with the appropriate amount of inoculum results in coalescing lesions on the leaf with the ultimate abscission of that leaf.
• Colonies of ChA 02W and ChA 02FF attained a diameter of 39-40 mm on oatmeal agar after 8 days at 27°C.
• Colonies of the same fungal strains attained diameters of 27-29 mm on malt extract agar.
• the fungus appeared as a dark mat of appressed mycelium with dark pycnidia scattered about the central portion of the colony.
• the upper side of the colony had an olivaceous colour while the reverse side was greenish-glaucus to olivaceous in colour.
• the pycnidia On inoculated lamb's-quarters stems the pycnidia attained a diameter of approximately 200-275 ⁇ m.
• the conidia were usually 20-25 ⁇ m X 7.5-10 ⁇ m.
• This example illustrates the production and preparation of inoculum for spraying onto lamb's-quarters.
• strains were stored in a refrigerator as oil-­covered vials.
• starter or seed cultures were begun by placing a small piece of mycelium from the storage culture onto the centre of a petri plate.
• the medium used for the starter culture was either Torula Yeast Agar [15 g/L torula yeast, 1 g/L K2HPO4, 0.5g/L MgSO4.7H2O, 20 g/L agar, and 100 mg/L novobiocin] or a mixture of 1/2 strength Torula Yeast Agar and 1/2 strength Potato Dextrose Agar [19.5 g/L potato dextrose agar, 7.5 g/L torula yeast, 0.5 g/L K2HPO4, 0.25 g/L MgSO4.7H2O, 10 g/L agar, and 100 mg/L].
• Torula Yeast Agar 15 g/L torula yeast, 1 g/L K2HPO4, 0.5g/L MgSO4.7H2O, 20 g/L agar, and 100 mg/L novobiocin
• Potato Dextrose Agar [19.5
• a needle was used to transfer a mixture of pycnidia and conidia from the seed culture to the production plate. To facilitate better coverage of the plane, separate colonies were begun at three locations on the plate.
• the production plates were harvested after two to three weeks of growth in a cabinet set for 12 hours of darkness followed by 12 hours of fluorescent and near-U.V. light. Temperature was 24°C during the light period and 22°C during the dark period. The following procedure was developed for harvesting the conidia:
• conidia production ranged from 3.7 X 106 to 1.2 X 107 conidia/plate.
• This example illustrates the effect of plant age and inoculum concentration on disease development.
• transplants of age 5 days, 10 days, and 15 days were sprayed at rates of 1.6 X 107 conidia/m2,3.1 X 107/m2, 6.3 X 107/m2, 1.3 X 108/m2, 2.5 X 108/m2,5 X 108/m2, 1 X 109/m2, and no conidia/m2.
• Each treatment consisted of a 12.5 cm pot containing 5 plants. Each treatment was replicated six times. After spraying, the plants were subjected to leaf wetness period of 20 hours at 22°C. The plants were then placed in a growth cabinet set at 22°C day/16°C night with a 14 hour photoperiod. Height and dry matter production were measured 14 days after spraying.
• This example illustrates the effect of leaf wetness duration and air temperature during the first 24 hours of the infection process on disease development.
• Transplanted lamb's-quarters at the 4-leaf stage were sprayed at a rate of 1 X 108 conidia/m2.
• the plants were placed in one of four dark growth cabinets.
• the growth cabinet temperatures were set at 12°C, 18°C, 24°C and 30°C.
• Leaf wetness was maintained by placing plants in moistened plastic bags for the duration of their leaf wetness periods of 0, 6, 12, 18 and 24 hours. Therefore, the experiment was a 5 X 4 factorial.
• Each treatment combination consisted of 5 transplants per pot, and was replicatred four times. Twenty-four hours after spraying, the plants were transferred to a growth cabinet at 22°C day/16°C night with a 14-hour photoperiod.
• the percentage leaf area affected 16°C night with a 14-hour photoperiod The percentage leaf area affected by disease was evaluated 8 days after spraying. Height and dry matter were measured 14 days after spraying. The means of each treatment combination, averaged over 4 replications, are presented in Tables 7, 8 & 9.
• This example illustrates the effect on triazine resistant and triazine susceptible lamb's-quarters plants when the Ascochyta pathogen is used in conjunction with atrazine.
• Each treatment combination was used on triazine susceptible and triazine resistant plants. There were 3 replications. After spraying, the plants were placed in a 22°C leaf wetness chamber for 20 hours. They were then placed in growth cabinets set at 22°C day/16°C night with a 14 hour photoperiod. Observations were made 8 days after treatment (Table 10).
• This example illustrates the host specificity of the pathogen, by spraying test species in the genus Chenopodium , economic species in the family Chenopodiaceae, and common unrelated crop species in which Chenopodium album can be found as a weed pest.
• test plants were placed in a 12.5 cm pot. One pot of the test species was sprayed with the pathogen while a second pot containing the same species was sprayed with water. A lamb's-quarters plant was included to check for the efficacy of the inoculum. Test plants were sprayed with the pathogen at a rate of 108 conidia/m2. After spraying, all plants were subjected to a leaf wetness period of 20-24 hrs. After this period, the plants were placed in either a growth chamber or the greenhouse. One to 2 weeks after treatment, plants were checked and compared with their controls to determine if they were susceptible to the pathogen. Plant response to the pathogen was rated as susceptible (S), resistant (R) or immune (I).
• S susceptible
• R resistant
• I immune

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• Microbiology (AREA)
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• Pest Control & Pesticides (AREA)
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• Agronomy & Crop Science (AREA)
• Plant Pathology (AREA)
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• Breeding Of Plants And Reproduction By Means Of Culturing (AREA)

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• 1987
  • 1987-06-16 CA CA000539789A patent/CA1324775C/fr not_active Expired - Fee Related
• 1988
  • 1988-06-02 US US07/201,211 patent/US4915724A/en not_active Expired - Fee Related
  • 1988-06-14 EP EP88401472A patent/EP0296057A3/fr not_active Withdrawn

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